**2. Numerical Method**

The simulation was conducted on ANSYS Fluent 18.1 (Ansys Inc., Canonsburg, PA, USA) with the shear stress transport (SST) *k* − ω viscous model. The compressible ideal gas condition was applied by using the density-based implicit solver. The viscosity was assumed as the Sutherland model, in which the viscosity varies only with temperature.
